DESCRIPTION: The purpose of this investigation is to develop a conceptual model to facilitate the optimal neurodevelopmental timing of epilepsy surgery for patients with complex partial seizures of temporal lobe origin, the most common candidates for focal resection (anterior temporal lobectomy). This study investigates the degree to which increasing duration and severity of epilepsy are associated with: 1) the presence and degree of anatomic abnormality (atrophy) in neural regions outside the primary (ipsilateral) epileptogenic hippocampus, 2) the presence and degree of impairments in contralateral memory function and generalized neuropsychological ability, both suggesting damage to neural regions outside the primary (ipsilateral) epileptogenic hippocampus, and 3) degree of impairment to health-related quality of life. Subject groups include: 1) 150 patients with early (< 14 years) age of recurrent onset of complex partial seizures between the chronological ages of 14-40 years, thus with considerable variability as to the duration and severity of epilepsy; and 2)75 age and sex matched controls. Patients and controls will undergo quantitative MRI volumetrics of selected regions of interest, comprehensive neuropsychological assessment, evaluation of health-related quality of life, and standardized interview. It is hypothesized that increasing duration but especially severity of epilepsy (e.g., years of epilepsy without sustained periods of remission, episodes of status epilepticus, lifetime number of secondary generalized tonic-clonic seizures) will be significantly associated with evidence of anatomic, neuropsychological, and health-related quality of life impairments.